Apparatus for on-line continuous chlorine analysis in turbid water and process streams

Abstract

The invention is directed towards methods and apparatus for accurately detecting the presence and concentration of an oxidant in a turbid water sample. This method is very helpful in allowing accurate and efficient (not too much nor too little) amounts of microbe killing oxidants to be introduced to water supplies that require oxidants but which at present cannot be measured properly. The method comprises the steps of: passing the water through at least one filter array, passing the filtered water to an analyzer, and then returning from the analyzer a measurement of the concentration. The filter array comprises at least one filter constructed and arranged to remove turbidity inducing material but not oxidant from the water sample. The analyzer can be a commonly commercially available analyzer that currently cannot accurately measure the oxidant concentration if the water had not been so filtered. This method allows users to apply easily available oxidant measuring technology to applications such as paper mill water where it is needed but was previously was not applicable.

What is claimed is: 
     
       1. A method of accurately detecting the presence and concentration of chlorine in a turbid water sample, the method comprising the steps of:
 passing the water sample through at least one filter device at an entry rate, 
 then passing the water sample into a sample buffer tank, and then on to a chlorine monitor, the sample tank constructed and arranged to pass water on to the monitor at an exit rate, 
 detecting the presence and concentration of chlorine in the water sample with the chlorine monitor; 
 wherein at least some of the time, the exit rate is different than the entry rate, 
 wherein a fluid sprayer is in communication with the filter device, the fluid sprayer is constructed and arranged to pass a spray fluid into the at least one filter device in a direction opposite to that which the water sample exits the filter device, the fluid is water, biocide, gas, or any combination thereof; and 
 wherein the at least one filter device is distal to a distal member, the filter device has in fluidic communication a sealable entry port in fluidic communication with the distal member, an exit port, and a sealable draining port, the draining port is proximal to the exit port and is distal to the entry port, wherein when spray fluid enters the filter device through the exit port the entry port is sealed and the draining port is opened and thereby if the spray fluid removes cake from the second filter device the cake does not come into contact with the distal member, wherein when the entry point is open sample water can pass from the distal member to the filter device, the distal member is another filter device, a pump, a conduit, or a sample water source. 
 
     
     
       2. The method of  claim 1  in which there are a series of two or more filter devices the filter devices constructed and arranged to remove turbidity inducing material but not chlorine from the water sample, the filter devices in fluidic communication with each other and are sequentially ordered to progressively apply an ever more fine degree of filtration as the sample moves distally. 
     
     
       3. The method of  claim 2  in which the sample tank comprises a high level point and a low level point and has at least one sensor array which can determine if the water surface in the sample tank is above the high level point in which case a drain port in the tank is opened to drain out water, and if the water surface in the sample tank is below the low level point in which case the drain port in the tank is closed to raise the water surface, the sensor array comprises at least one sensor that can determine if the water surface is located by at least one of the level points. 
     
     
       4. The method of  claim 1  in which at the time that the entry port is sealed, sample water is still continuously flowing at a constant rate to the monitor. 
     
     
       5. The method of  claim 4  in which the times at which the spray fluid is passed into the at least one filter device is coordinated to assure that the spray fluid flow will cease and that the sample water will again pass through the at least one filter device before the water surface drops below the low level point. 
     
     
       6. The method of  claim 1  in which the entry flow rate is sufficient for effective filtration but is incompatible with the flow rate requirements for proper operation of the monitor. 
     
     
       7. The method of  claim 1  in which the flow exit flow rate is sufficient for proper operation of the monitor but is incompatible with the flow rate required for effective filtration of the sample water. 
     
     
       8. The method of  claim 1  in which the water sample is water from a paper mill process stream, clarified process water, influent, effluent, wastewater, or any combination thereof. 
     
     
       9. The method of  claim 1  in which the turbidity inducing material is selected from the list consisting of: cellulose fibers, mineral fillers, property enhancing polymers, sizing agents, wood chips, silica, glass fibers and any combination thereof. 
     
     
       10. The method of  claim 1  in which the filtered water sample is also monitored to measure one item selected from the list consisting of: concentration of a non-chlorine oxidant, pH, oxidation reduction potential, peroxide content, sulfite content, and any combination thereof. 
     
     
       11. The method of  claim 1  in which the filtration of the water sample prevents the monitor from providing an erroneous measurement of chlorine in the sample. 
     
     
       12. The method of  claim 1  in which the filter device comprises a surface having a plurality of pores sized to allows the passage of chlorine bearing water but to catch at least some turbidity causing matter on the surface as cake. 
     
     
       13. The method of  claim 1  in which the filter device comprises a surface having a plurality of pores sized and positioned to allows the passage through it of chlorine bearing water but to catch at least some turbidity causing matter on the surface as cake and the surface is located in fluidic communication with and distal to the entry port and proximal to the exit port.